1. Field of the Invention
The present invention relates to a complex material formed by joining electrodes to both surfaces of an ion conduction film, and more particularly, to a complex material capable of causing curve and deformation thereof by using a potential difference. More specifically, the present invention relates to a complex material formed by joining conductive cloths as electrodes to both surfaces of an ion conduction film. The complex material of the present invention is superior in deformation force and quick response property, has a large degree of freedom for a shape, and has a high strength and durability necessary for practical use. In addition, the complex material of the present invention is excellent in an economic aspect.
2. Description of the Related Art
A technology of generating curve and deformation on an ion conduction film which involves providing electrodes on both surfaces of the ion conduction film and applying potential difference to the electrodes is already proposed. A complex material having the electrodes provided on both surfaces of the ion conduction film has a simple structure, so the miniaturization thereof can easily be made. Further, the complex material operates with small electric power, so the complex material can be used as an actuator element.
For example, JP 07-4075 B proposes a method in which films formed on both surfaces of the ion exchange film coated with noble metal by plating and the like are used as electrodes, and a weak voltage of several volts is applied to the electrodes to move electrolyte in the film, to thereby deform the film on the basis of a swelling difference between front and rear surfaces. Also, EAMEX Corporation proposes a complex material, in which gold as an electrode is chemically plated on an ion exchange resin, as an actuator element (refer to JP 2004-197215 A and JP 2005-187926 A).
However, in the conventional technology of forming the electrode metal films on both surfaces of the ion conduction film by using plating and the like, the metal films that are short of softness and flexibility are formed on both surfaces of the ion conduction film. Thus, there has been a drawback in that because the curve and deformation of the ion conduction film are liable to be suppressed, a sufficient deformation force and quick response property are difficult to obtain.
In other words, the complex material of the ion conduction film and the electrode metal film is thick. Thus, when a curve is to be generated on the complex material, a difference in length is generated between inner and outer surfaces of the curve. In short, the coated film on the inner surface is required to be contracted, or the coated film on the outer surface is required to be expanded. However, although the ion conduction film has stretchability, softness, and flexibility necessary for the deformation in a wet state, the metal film is poor in stretchability and the flexibility. Thus, when the complex material is deformed, there has been a case where the metal film acted as a resistance and weakened the deformation force, to delay a deformation speed.
In particular, as the metal film thickness of the electrode and the ion conduction film thickness increase, this tendency becomes prominent. Thus, it has been difficult to increase the deformation force by making the ion conduction film thick. As a result, there have been such problems that large deformation cannot be followed, the deformation force is weak, a reaction is slow, and the like.
Also, there have been problems with regard to practicability and durability. The conventional technology uses characteristics in which the ion conduction film is curved when a potential difference is applied to the electrode metal films provided on both surfaces of the ion conduction film, the ion conduction film returns to its original state when the application of a voltage is released, and the ion conduction film is curved in an opposite direction when an opposite potential is applied. By properly selecting and repeating those changes in states in accordance with an object, the object can be consequently attained.
However, the conventional technique has such a tendency that a metal thin film short of bending durability is fractured by the repetition of large deformation and bending. The metal film provided as the electrode is required to be formed as thin as possible so as not to suppress the curve and deformation of the ion conduction film. Thus, this tendency becomes more and more prominent.
Also, when the ion conduction film is made thick in order to increase the deformation force, a dimensional difference between the inner and outer surfaces becomes great when being curved. Thus, a force applied to the metal film as the electrode becomes stronger, and the curve and the deformation become more and more difficult to be generated, leading to the metal film being easily fractured. When the metal film of the electrode is made thicker in order to prevent the fracture, the curve and the deformation become difficult to be generated, which results in that the object cannot be attained.
Moreover, in a configuration in which the metal thin films as the electrodes are provided on both surfaces of the ion conduction film, it has been difficult to obtain the characteristics as the complex material necessary for practical use, such as tensile strength and abrasion strength sufficient for practical use. In short, it has been impossible to obtain performances sufficient for enduring stress applied to the complex material in practical use, such as tension, bending, shearing, and abrasion. In other words, for example, many metal films used for the conventional electrodes are poor in stretchability, and when the complex material is expanded by about 10%, the metal film is fractured to be useless as the electrode. In particular, this tendency is severe in the electrode metal film obtained by plating.
As described above, in the conventionally-proposed technique, materials and thicknesses and the like of the electrode and the ion conduction film are required to be limited in order to obtain a sufficient curve and deformation when a voltage is applied. Thus, it has been impossible to obtain a sufficient improvement of durability against stresses such as tension, bending, shearing, and abrasion.
Also, in order to obtain an intended curve and deformation, there has been a limit on a shape of the complex material. In a case of applying the potential difference to both surfaces of the ion conduction film and moving the electrolyte in the film to generate the swelling difference between both surfaces of the film, to thereby generate the curve, for example, when a deformation as shown in FIG. 2 is to be made, the complex material is required to be a rectangle, preferably a rectangle in which a difference between a long side and a short side is large. If a voltage is applied to both surfaces of a square, the deformation caused by the swelling is generated at four corners of the square, and the deformation shown in FIG. 2 cannot be expected. Also, the curve in the case of the rectangle is generated in the long side direction and is never generated in the short side direction. In this way, in the conventional technique, the shape of the complex material is limited, resulting in limiting usage and application. Thus, it has been difficult to devise such a method of increasing the width to increase the curving force.
Also, formation of the electrodes on both surfaces of the ion conduction film by plating and the like requires a number of steps and time. Thus, an improvement in terms of cost has also been an object to be achieved.